I have just seen this snippet of the recent Argentina-Colombia match in which James (Colombia #10) deliberately pushes his own teammate Torres (Colombia #16) to get to the ball.
https://www.youtube.com/watch?v=qA4Ix9TsxLQ
The referee's call in this particular case was clearly incorrect (he gave an free kick to Colombia because he believed that Biglia, Argentina #6, who didn't actually do anything, was the one to cause Torres to fall).
But what would the correct call have been? More generally, if you foul your own teammate, do the Rules of the Game allow the referee to award the opposite team a free kick? Can you even be yellow-carded or red-carded for such an action?